Hypoid gear lubricants for slip-lock differentials



United States Patent 1 O 3,211,653 HYPOID GEAR LUBRICANTS FOR SLIP-LOCKDIFFERENTIALS Rosemary OHalloran, Union, N..l., assignor to EssoResearch and Engineering Company, a corporation of Delaware No Drawing.Filed Dec. 31, 1958, Ser. No. 784,044 1 Claim. (Cl. 25250) Thisinvention relates to the discovery that certain amines or aminederivatives when added to gear lubricants, eliminate or markedly reducethose noises which frequently occur in the clutch plate assembly of thenewly introduced slip-lock differentials for automotive vehicles. Thisinvention also relates to the discovery that gear oil blends designedfor very severe operating conditions (high speed, high torque or severeshock) may be rendered suitable for use in slip-lock differentialswithout objectionable noise and without any loss in extreme pressureproperties by the addition of minor amounts of an amine and anazomethine. This invention therefore relates to a method for eliminatingthose noises which frequently occur in conventionally lubricatedslip-lock differentials and to the gear lubricating compositionssuitable for use in slip-lock differentials that are produced thereby.

There is a wide variety of conventional gear oils entirely satisfactoryfor lubricating differentials. However, when these conventional gearoils are used to lubricate slip-lock differentials, in many cases anoisy chattering occurs in the clutch plate assembly of the slip-lockdifferential under certain conditions which occur in normal driving. Theslip-lock differential units for automotive rear axles consist of a packof 3 to 5 discs or plates mounted on each axle which act to retard themovement of the faster running wheel (as when one wheel is slipping onmud or ice) and to direct torque back to the other wheel, i.e., when onewheel begins to slip, the clutch plates upon that axle are engaged toretard the movement of the slipping wheel and thus direct torque to thenon-slipping wheel. This enables the car to move in situations where aconventional differential would continue to allow the torque to betransmitted to the slipping wheel. It has been found through testing onnumerous cars equipped with these slip-lock differentials that on sharpturns the clutch of the axle of the wheel on the outside arc of the turnwill be partially engaged causing chattering and thudding sounds thatcreate a vibration throughout the entire car. This noise and vibrationoccurs frequently enough in general car operation to be annoying to thedriver and disturbing to the automobile manufacturers. Properlubrication of the slip-lock axles requires a lubricant containing (a)an extreme pressure agent to prevent wear of the highly loaded hypoidgears and (b) a lubricant which will prevent or reduce the noise of theclutch plates when they are engaged and especially when they arepartially engaged as when making sharp turns.

It has now been found and this finding forms the basis of the presentinvention, that certain amines or amine derivatives when added to gearoils completely removes or markedly reduces this objectionable clutchplate chatter. These amine-gear oil blends continue to give entirelysatisfactory performance in standard differentials in addition to givingquiet performance in the newly introduced slip-lock differentials. Theamine additives of this invention are particularly effective in gearoils compounded from lubricating oils having a visocity of about 50 to220 SSU at 210 F. and containing extreme pressure additives such assulfur-chlorine and PS-Cl containing compounds. However, in gear oilsdesigned for extremely severe operating conditions (high speed, hightorque or severe shock) as are gear oils designed for use in militaryvehicles (i.e., gear oils passing MIL-La2105 and more severe tests), thelamines of this invention have been found to reduce the ability of thesegear oils to pass severe gear tests. Thus, as a further facet of thisinvention it has been found that addition of an azomethine in additionto the amine will improve the ability of these high performance gear oilblends to pass severe gear tests of the type required for militaryapproval. At the same time the amine-azomethine blend imparts quietperformance to these high performance gear oils when used in sliplockdifferentials.

In brief compass, the slip-lock differential lubricants of thisinvention will comprise a major proportion of a gear oil compounded froma lubricating or base oil having a viscosity of about 50 to 220 SUS at210 F., an extreme pressure additive, and in the range of 0.2 to 2.0 wt.percent of a primary C to C alkyl amine. The sliplock differentiallubricants designed for extremely severe operating conditions (highspeed, high torque or severe shock) will comprise in the range of 0.15to 1.5 Wt. percent of a C to C aliphatic azomethine in addition to theabove ingredients, the ratio of amine to azomethine being about 0.25 to4.0.

The amine additives of this invention include primary alkyl amines,wherein the alkyl group is a branched or straight chain alkyl group of aC to C hydrocarbon. A mixture of primary alkyl amines may also be used,such as the primary alkyl amines made from hydrogenated tallow. Examplesof operable amines are octadecyl, hexadecyl, octadecenyl and dodecylamines. The primary alkyl amines of 12 to 24 carbon atoms are preferred,and mixtures of the primary alkyl amines made from hydrogenated talloware particularly preferred.

The azomethine additive is prepared by reacting formaldehyde with analiphatic amine and has the following generic formula:

wherein R represents an alkyl or alkenyl group of 12-24 carbon atoms andpreferably 14 16 carbon atoms. Particularly preferred are theazomethines, wherein R is a tertiary alkyl group of 1416 carbon atoms.The preferred species of R is derived from propylene polymer. Thereaction between the alkyl amine and formaldehyde is shown in thefollowing equation:

Suitable azomethines have a carbon to hydrogen ratio of about 526, anitrogen content between 5.5 and 7% by weight and carbon content betweenand by weight by ultimate analysis.

The base oil used to form the gear lubricants of this invention may beeither a mineral or a synthetic lubricating oil, the former beingpreferred. These lubricating oils will have a viscosity in the range of50 to 220 SUS at 210 F. and a viscosity index in the range of 20 to+150, preferably in the range of 60 to 100.

The gear oil for use in accordance with this invention may containconventional additives, such as viscosity index improvers anti-oxidantsor corrosion inhibitors, and normally contains extreme pressure agents,such as chlorinated parafiins, lead soaps, zinc dialkyl dithiophosphate,sulfurized oils, etc. Extreme pressure additives are well known in thelubricating art and are normally used in hypoid gear lubricants. Theincreased rear Wheel torque of new passenger cars and commercialvehicles has caused a corresponding increase in the loading on thehypoid gears and has necessitated the use of lubricants containingextreme pressure agents.

The additives of this invention may be prepared in concentrated form.For example, about 2 to 20 Wt. percent of the amine or 2 to 20 wt.percent of the amine and 1.5

to 15 wt. percent of the aliphatic azomethine may be added to a gear oilbase to form the concentrate.

In general, the compositions of this invention will be prepared bysimply adding the amine or the amine and azomethine to the gear oilbase.

The invention will be further understood by the following examples whichinclude the preferred embodiments of the invention.

EXAMPLE I To show that certain amines or amine derivatives substantiallyreduce or eliminate those noises which frequently occur in slip-lockdifferentials, a mineral lubricating oil (base oil) and three differentgear oils were tested with and without the amine additives in differentmake automobiles equipped with slip-lock differentials. A conventionallylubricated slip-lock differential produces frequent and extremelyannoying chattering sounds during normal operation, however, for testpurposes the most severe conditions are used so that the noise is at itsworst level. Thus, changes in noise level may be apparent. Data inTables I and III which follow were obtained under the most severeconditions. Data in Table II are representative of a variety ofrelatively severe conditions to show graduations of performance.

The oils used in the following tests were:

Base Oil.A mineral lubricating oil having a viscosity at 210 F. of about94 SUS and a viscosity index of 90 consisting of a blend of (1) dewaxed,deasphalted residuum having nominal viscosity at 210 F. of 210 SUS and(2) dewaxed, phenol extracted clay-contacted distillate of 4 erallubricating oil having a V.I. of and a viscosity at F. of 1094 SUS. Thesulfur chlorinated parafiin was prepared according to U.S. 2,124,598 andcontained 30 wt. percent chlorine and 6 wt. percent sulfur. The zincdihexyl dithiophosphate used above was prepared according to U.S.2,369,632.

Gear Oil B.A hypoid gear lubricating oil composition consisting of 10wt. percent of the sulfur-chlorinated parafl in of Gear Oil A in theabove Base Oil (Viscosity Index of 90 and a viscosity at 210 F. of 94SUS).

Gear Oil C.-A hypoid gear lubricating oil consisting of 3.05 wt. percentof the sulfur-chlorinated paraffin of Gear Oil A and 2.48 wt. percent ofthe zinc dihexyl dithiophosphate of Gear Oil A in the above Base Oil(Viscosity Index of 90 and a viscosity at 210 F. of 94 SUS).

Table I which follows shows, first, that slip-lock differentials arenoisy with, (1) base oils (Run 1), (2) conventional sulfur-chlorinatedtype gear oils (Gear Oil B, Run 3, and (3) with MIL-L-2l05 type oils(Gear Oil A, Run 7); second, that certain conventional lubricity oroilness agents do not improve performance (Runs 4, 5, 8, 9, 10 and 11);third, that Amine T (a mixture of primary alkyl amines consisting of 30%hexadecyl amine and 70% octadecyl amine) gives marked reduction orcomplete elimination of noise (Runs 2, 6, 12 and 13); and, fourth,

- that a mixture of Amine T and Azomethine J (a C alkyl azomethine) isalso effective in markedly reducing noise (Run 14).

The road tests of Table I were conducted by executing tight circles atspeeds of from about 2 to 10 miles per hour with braking during thecourse of the turn.

Table I Noise on sharp turn with braking Runs Additive, wt. percent GearOil 58 Chrysler 58 DeSoto '58 Pontiac None Base oil Severe 1% wt. AmineT- None None. Severe. 0.25 wt. percent TOP..- Do. 0.5 wt. percent TOPDo. 0.5 wt. percent Amine T.-. None.

acid.

25 wt. percent sullurized Sperm 011-. 0.5 wt. percent castor oil 0.25wt. percent dimerized linoleic 0.5 wt. percent TOP 1.0 wt. percent AmineT A 0.5 wt. percent Amine T 0.3J3 Amine T plus 0.14 Azomethine Verylight-" Trace nominal viscosity at 100 F. of 250 SUS, each componentbeing derived from Mid-Continent crude.

Gear Oil A.A base hypoid gear lubricating oil composition prepared bymixing 6.4 wt. percent of a sulfurchlorinated paraffin and 5.2 wt.percent of a zinc dihexyl dithiophosphate (the hexyl groups were derivedfrom methyl isobutyl carbinol) in 88.4 wt. percent of a min- Table II[All tests were made in the same 1958 Chrysler within a one week period.Each oil was used for at least 7 miles before start of testing]Slip-lock noise rating Leit circles Right circles Auxiliary additive,Gear Oil wt. percent Deceleration Slow Heavy Slew drag deceleration dragMedium Heavy None A Severe Severe Severe Moderate.-. Moderate. Amine TA- Very light Amine S l A Severe Severe Trace. Amine salt D 2 A. .do .dndo D0.

1 Soya dimethyl amine, i.e. a tertiary amine RN(OH 2 Diolcate ofN-tallow propylene diamine.

Table III shows the ability of various amine additives in variedconcentrations to suppress slip-lock chattering. The table also showsthat while azomethine by itself is not effective in preventing noise inslip-lock differentials, it performs satisfactorily when combined withprimary alkyl amines. Further, the table establishes that amines andparticularly primary amines in concentrations above 0.3 wt. percentbased on the weight of the gear oil blend, either alone or incombination with alkyl azomethines will substantially reduce chatteringin slip-lock differentials. The tests are particularly designed todetermine the ability of the additive to suppress the chattering noiseswhich occur on sharp turns at speeds of about 5 to 15 miles per hour.Partial engagement of the clutch plates on the axle of the outside wheel(relative to the turn) occurs under these conditions.

EXAMPLE II As pointed out in the specification amine containing gear oilblends are not quite as good in extreme pressure properties as theoriginal gear oil. That is, addition of a primary amine causes a slightincrease in wear as do other amines and amine derivatives. However,azomethine reduces wear and when added to a-mine/ gear oil of 3.4 to 1between the test cylinders and the shaft. The weight loss, inmilligrams, of the test cylinders was then measured.

Table IV MODIFIED SAE TEST [15-minute break-in with 55-pound load, (plus1 hour at 225 F. with 100-pound loa Wt. Percent Wt. loss of rings, mg.Additive in GDar Oil Top I Bottom None 0 63 15 Amine T 0.5 Amino D 1.0253 27 Dioleate of A 1.0 102 84 Oleic acid 0.25 123 34 Dimer of linoleicacid 0. 154 20 Azomethine .T 0. 5 10 10 Amine T 0.5

and 11 12 Azomethine .I 0.5 Amine T O. 7

and 18 20 Azomethine J 0. 3

1 Sparks, heavy scoring.

2 Amine D is an N alkyl propylene diamine wherein the alkyl group iscomposed of a mixture of C to 0.5 alkyl groups and a C mono-unsaturatedchain (sold cornmercially as Duomeen T).

3 Same5 as Amine Salt D of Table II (dioleate of N-tallow propyleneblends imparts a wear resistance superior to that of the 25 diamme TableIII SLIP-LOCK DIFFERENTIAL NOISE TESTS Noise on Left Circles withBraking Additive Gear 011 Wt. percent in gear oil 58 DeSoto 58 Chrysler58 Chev. 58 Olds.

N one Severe Severe Severe Severe. Amine salt D Amine T Do Do DoModerate. Azomethine J Amine T and Very light Azomethine .T 0. 25 AmineT O. 7

and N n None. Azomethine J 0.3 Amine T 0.33

and Trace Azomethine .T 0. 14

gear oil without amine despite the adverse effect, as regards wear, ofthe amine when used alone in the gear oil.

Table IV shows that the amines of Table II when added to highperformance MIL-L-ZlOS type gear oils, will reduce the extreme pressureproperties of said gear oils. The table further shows, however, that ifan alkyl azomethine or a combination of an alkyl azomethine and an amineare added to the same gear oil the extreme pressure properties, insteadof being decreased, will actually be improved.

Table IV represents the results obtained in a modified SAE test. Thebase lubricant for this test was a hypoid gear oil, hereinafterdesignated Gear Oil D, which is. the same as Gear Oil A except that 6.9wt. percent of the sulfur-chlorinated paraifin and 5.7 Wt. percent ofthe zinc dihexyl dithiophosphate were added to the base oil. The extremepressure properties of Gear Oil D were tested alone and with differentadditives by means of an SAE Extreme Pressure Testing Machine (CRCdesignation, L-17-545). See Coordinating Research Councils Handbook,1946; copyright 1946, by Coordinating Research Council, Inc., andpublished by J. I Little and Ives Company, New York. In brief, this testconsisted of rotating two cylindrical test specimens in line contactwith each other and in opposite directions with pressure applied at theline contact between the rotating cylinders. A SS-pound load was appliedfor a 15-minute break-in period, followed by increasing the load to 110pounds and rotating the test cylinders for one hour at 225 F. The shaftwas operated at 500 r.p.m. with a gear ratio To confirm the laboratorydata of Table IV full-scale gear tests were conducted on Gear Oil Aalone and on Gear Oil A containing those additives which success fullyprevented chattering noises in the road tests of Tables I, II and IIIabove.

The full-scale gear tests consisted of:

(I) CRC-L-37-756 high speed-high torque test.The CRCL37-75 6 test wasdeveloped for the Ordnance Department and is titled Research Techniquefor Determining Load-Carrying, Wear, and Extreme PressureCharacteristics of Universal Gear Lubricants in Axles Under Conditionsof High-Speed, Low-Torque Operation, Followed by Low-Speed, High-TorqueOperation. Briefly described, this test is carried out as follows:

The test unit consists of a new %-ton army truck hypoid rear axlecarrier, 5 .83: 1 ratio, installed in its own housing. The unit isdriven by a six-cylinder 235 cu. in. Chevrolet truck engine withstandard ignition and carburetor, with suitable transmission, couplings,and dynamometer parts.

Sequence 1 of the test consists of minutes operation at a ring gearspeed of 440 :5 r.p.m. and a ring gear torque of 9460 i inch-pound. Thegear oil temperature is 300 F. maximum.

Sequence 2 of the test consists of 24 hours operation at a ring gearspeed of 80 :1 r.p.m. and a ring gear torque of 41,800 i150 inch-pound.The oil temperature is 275 -F. 13 F.

After completion of the above test, the ring and pinion gears areexamined for evidence of surface distress and 7 wear. The results of theabove tests are shown in Table V which follows.

(2) Buick 10-A road test.The Buick lO-A test is an actual road test andconsists of 10 high-speed cycles of driving from 60 to 109 m.p.h., 3shock cycles at 50 to 35 mph, 60 to 45 rn.p.h., and 70 to 55 m.p.h.,respectively, followed by 10 more high speed cycles of 60 to 109 m.p.h.The high speed cycles were carried out by rapidly accelerating from 60to 109 mph, then allowing the auto to coast until the speed was back to60 mph, then the cycle was repeated. The shock cycles were carried outby allowing the auto to coast from the higher speed until the lowerspeed was reached and then shifting into low gear. Upon completion oftest, the differential was disassembled and the ring and pinion gearsexamined for scoring.

Table V FULL-SCALE GEAR TESTS Buick 10-A road shock test, percent scoreTest oils, additives, wt. percent in Gear Oil A C RC-L-37 test,highspeed, high-torque None. Very light ridging 5-10 (interpolated). 0.5Amine T Fail, light ridging Pass, 5. 0.5 Amine T+0.25 tri- Fail, mediumridging Borderline, 10.

eresyl phosphate. 0.7 Amine T plus 0.3

Azoinethine J.

0.5 Amine '1 plus 0.25

Azomethine J.

0.5 Amine T lus 0.5 dioetyl aci phosphate.

Pass

Pass, 3.

Fail, light-medium ridging.

The above table shows that only the additive of the present invention(i.e., the combination of a primary amine with an alkyl azomethine),when added to gear oils, will both suppress the noise characteristic ofsliplock difierentials and impart extreme pressure properties to thegear oil.

EXAMPLE 111 Table VI GEAR OIL OXIDATION TESTS [100 hrs. at 250 F.]

It is evident that the additives of this invention, when used in totalconcentrations of 0.75 to 1.0% in Gear Oil A, are effective not only incontrolling the increase in viscosity but also in preventing theformation of sediment upon oxidation.

In summary, Examples I-III show that addition of minor amounts of anamine will suppress the noise in sliplock differentials, reduce sludgeformation on storage, and when combined with an azomethine will improvethe extreme pressure properties of the lubricant.

Use of the additive and additive combination of' this invention shouldnot be limited to the above examples.

What is claimed is:

A method for reducing chatter in a limited slip differential gearassembly which comprises lubricating the assembly with a gear lubricantconsisting essentially of a base mineral oil of lubricating viscosity,about 5 to 20 percent by weight of total extreme pressure agent and 0.2to 1.0 percent by weight of primary C to C alkyl amine.

References Cited by the Examiner UNITED STATES PATENTS 1,594,983 8/26Somerville 252 1,888,023 11/32 Adams 25250 X 2,268,608 1/42 'McNulty etal. 25247.5 X 2,366,013 12/44 Duncan 25247 X 2,696,473 12/54 Sokol25247.5 X 2,758,086 7/56 Stuart et al. 25250 X FOREIGN PATENTS 757,2199/56 Great Britain.

DANIEL E. WYMAN, Primary Examiner.

J'ULIUS GREENWALD, JOSEPH R. LIBERMAN,

Examiners.

